Paper Title
The Impact of Open Approach Learning Management on Mathematical Problem-Solving Skills and Academic Achievement in Basic Counting Principles among Grade 11 Students.

Abstract
This research aimed to 1)compare the ability to solve mathematics problems and academic achievement before and after learning the topic of Basic Counting Principles of Grade 11 students who were taught by traditional learning methods and open learning methods. The target groups of this research Grade 11 students at Phdungnaree School, Mahasarakham Province, in the second semester of the 2024 academic year, consisting of 2 classrooms and 75 students, selected by cluster random sampling as follows: 1) the experimental group, consisting of 40 students from Grade 11/3 who were taught using the Open Approach learning model for the topic of Fundamental Counting Principles, and (2) the control group, consisting of 35 students from Grade 11/12 who were taught using the conventional learning model for the same topic. The research instruments included: 1) Open learning management plans and normal learning management plans on the topic of Basic Counting Principles, 12 plans, total learning management time 12 hours; 2) a 5-question mathematics problem-solving ability test, which was a written subjective test; 3) a 30-question academic achievement test on basic counting principles, which was a 5-choice multiple-choice test;.The research results found that The ability to solve mathematical problems and academic achievement before and after studying the topic of Basic Counting Principles of Grade 11 students who received normal learning management and open learning management found that students who received normal learning management and students who received open learning management could solve mathematical problems and academic achievement after studying higher than before studying at a statistical significance level of .05, which accepted the research hypothesis that had been set. Keywords - Open Approach Learning, Model Problem-Solving Skills in Mathematics, Academic Achievement.